OTN (Optical Transport Network), which is recommended by the ITU (International Telecommunication Union), have been known as one of the standards for transmitting signals in an optical network (e.g., core network). In OTN, client data is stored in OTU (Optical channel Transport Unit) frames and is transmitted.
In recent years, further increases in speed have been needed in optical networks. In response to the need, for example, a frame generation apparatus that generates ODTU frames, a digital transmission system that provides flexible payload capacity in OTU, and a method of mapping any signals to SONET (Synchronous Optical Network) have been proposed. Note that Japanese Laid-Open Patent Application Publication No. 2010-212890, Japanese Laid-Open Patent Application Publication No. 2012-4839, and Japanese Laid-Open Patent Application Publication No. 2001-69104 are known as related art.
As described above, technologies to increase the speed of optical networks have been proposed. However, as the optical networks increases their speed, the size of a circuit that processes OTU frames increases and the power consumption may also be increased.